A dialyzer intended to be used as an artificial kidney is described by Abel, Rowntree and Turner in The Journal of Pharmacology and Experimental Therapeutics, Vol. V, 1913-1914, pp. 275-316. They passed blood taken from an artery of an animal through a number of tubular collodion membranes connected in parallel. Around the membranes there was kept up a flow of dialysate which served to discharge the low-molecular waste products extracted from the blood through the walls of the membranes. The purified blood was fed back to the animal through a vein.
Abel et al had thus laid the basis for the application of hemodialysis outside the body in the case of kidney deficiency. They realized that the use of tubular membranes offers considerable advantage, such as a favorable internal volume to surface area ratio. In this way there is formed a large exchanging membrane surface area in combination with a low blood volume and a short diffusion route, just as in the case of capillary blood vessels in kidneys.
The imitation of capillary blood vessels by artificially formed capillary membrane tubes has also been described by Huzella in Biochemische Zeitschrift 194,128 (1928).
A separating device comprising tubular membranes for isolating helium from gas mixtures is known from Bell Labs. Record, July 1958 No. 7, pp. 262-263, and French Patent specification No. 1,227,030.
There the membranes are formed by a bundle of glass tubes which have a high permeability for helium and a low permeability for other gases. For the separating power to be high the total surface area of the membranes should be large and their wall thickness small. To this end use is made of a very large number of fine, thin-walled glass capillaries, whose ends are embedded in supporting members of synthetic material. Owing to their very small diameter they are, in spite of their low wall thickness, resistant to large differences in pressure across their wall.
From the German Patent Application 1,226,988 laid open to public inspection there is known a separating device provided with spun capillary membranes, which may be used, inter alia, for hemodialysis.
In order that a largest possible membrane surface area may be obtained that may contribute to the exchange between the two media, the known devices of the type indicated above are so constructed that the tubular membranes are preferably not additionally supported in the space between the supporting members.